When it comes to "experts" a.k.a. The AAP (American Academy of Pediatrics) as well as nutritionists, giving juice to a baby or toddler is a no-no. Juice does not have much nutritional value and honestly, there is more nutrition in a fresh piece of fruit than a cup of juice; not to mention, juice is loaded with lots of sugar and kids today consume way more sugar than necessary. I believe the recommendation is no more than 4 ounces of juice for little under the age of 4. I actually am not a fan of juice myself; I'm more of a water drinker as I find juice too sickeningly sweet. I've worked in the childcare industry for many years and know many children personally who refuse to drink water and only drink juice because they were introduced to the sweet drink early in life. Not to mention, childhood obsesity is at an all-time high, so I can understand a reason to limit or not give juice at all.
Having a son who was labeled as overweight at 12 months old, I actually did not give him a single taste of juice until he was 18 months old and so sick that he refused to eat or drink a thing. Then, I put a splash (probably about a tablespoon or so) of white grape juice into his (9 oz size) sippy cup of water; J sucked that down dry and asked for more. For awhile, the rule was no juice unless J got sick because he's very picky when sick and having a child who is hydrated and not suffering from low blood sugar matters to me. Since then, I have loosened up a tad. J still mainly drinks water plus his 16 oz of Lactaid whole milk on a daily basis but if he is thirsty and has already had a lot of water and his milk, I give a splash of juice in his water. The way I see it, a tiny bit of juice does not contain much sugar and gives him some variety of flavor. The only other time we give juice is when we go out to eat since restaurants don't carry lactose free milk; in those instances I ask the server for a kid cup with mostly water and a splash of juice. They're always happy to comply and that ensures my little guy doesn't feel left out when Mama gives up her usual water for some iced tea and when Daddy has soda.
Once again, this is a personal matter but I do believe that my loosening up a small degree is good. J doesn't drink juice on a daily basis and he's slimmed down a lot, so I know he is a healthy guy. I'm curious to hear when my readers started giving juice and if their kids are water drinkers at all. :)